USA Without Fossil Fuel

Stephen Hibbs
November 28, 2010

This paper will look at how the United States Of
America could provide itself with the raw energy that it consumes, were
supplies of Coal, Natural Gas, Oil, and Nuclear Fissile Material to
disappear entirely. The reason for this discussion is because the
supplies of these materials are finite on the earth due to the fact that
they are either not created on earth, as in the case of radioactive
material, or take a very long time to be created from decomposed organic
material, as in the case of coal, natural gas, and oil. The problem with
using these fuels is that when they are used to produce energy, the raw
material that goes into the process (ie the coal, oil, or Uranium)
becomes largely useless after it has been used to produce energy, and
becomes an unusable waste product. However, were sources of energy such
as the sun or wind to be used, there would be no worry of source
depletion since that energy continues to be incident upon the earth at a
constant rate, whether or not humans capture it for use as electricity.

I will not concern myself here with how long it will
take for these sources of fuel to run out, but they will run out
eventually, given any nonzero rate of consumption. I also will not
concern myself with expected rates of consumption on future dates, or
expected improvements in current technologies. Lastly, I will not
discuss the environmental impact of any of these technologies. What I
will look at is the current energy budget of the United States as of
2009, meaning the total quantity of energy, in Joules, used by the
United States over the course of the year 2009. I will then look at some
of the most promising current technologies for electricity production
(as of 2010), that do not rely on the consumption of non-renewable
fissile material. From there, I will look into what scale of these
technologies would be needed in order to provide the United States with
the amount of energy that it currently uses, without the use of nuclear
fissile material or hydrocarbons. Lastly, I will discuss some of the
difficulties in incorporating those technologies with our current
infrastructure and usage patterns.

Source

Amount

%

Oil

842.9 Mtoe

35.4 × 1018 J

36.5

Natural Gas

588.7 Mtoe

25.7 × 1018 J

25.5

Coal

498.0 Mtoe

20.9 × 1018 J

21.6

Nuclear

190.2 Mtoe

8.0 × 1018 J

8.3

Hydro-electricity

62.2 Mtoe

2.6 × 1018 J

2.7

Solar

.097 × 1015 BTU

0.1 × 1018 J

0.1

Wind

.546 × 1015 BTU

0.6 × 1018 J

0.6

Geothermal

.336 × 1015 BTU

0.4 × 1018 J

0.4

Biomass

3.852 &times 1015 BTU

4.1 × 1018 J

4.2

Total

96.8 &times 1018 J

100

Table 1: 2009 US Energy Consumption

Current Usage And Production Sources

The United States energy consumption for 2009 is
shown in Table 1. The numbers for the large, traditional energy sources
in the top half of the table are taken from the 2010 BP Statistical
Review Of World Energy. [1] They are quoted in units of million tons of
oil equivalent (Mtoe). The survey states that 1 tonne of oil equivalent
is roughly equal to 42 gigaJoules of energy, so one Mtoe is just 4.2
× 1016 Joules. The number for the newer "renewable"
sources are from the US Department Of Energy. [3] These numbers have
larger error bars on them (especially geothermal and biomass) since it
is not always made clear what technologies are defined in each category.
From this table we can see that hydro-electricity, solar, and wind only
make up a small percentage (about 8%) of the total energy usage of the
United States. The other 92% of energy comes from fuels which will at
some point run out. Already we can see that going without these energy
sources will be a tall order!

Why We Use What We Use

On of the main reasons the United States (and the
rest of the world) relies on these sources so predominantly now is that
people are good at using them; we've been using these sources for a long
time, so the coal, oil, and natural gas we use are all relatively cheap
to get out of the ground, and the engines that burn them are fairly
efficient. But there is another very important reason the world uses
these materials, one that isn't as obvious- that we can (relatively)
easily control the rate at which we produce electricity with these
fuels, with the exception of nuclear energy.

The way the United States' electricity needs are
largely met is by providing a certain baseline amount of energy with
fairly constant supplies of nuclear energy (nuclear energy is hard to
turn on and off quickly) and by providing most other electricity by
burning a combination of coal, oil, and natural gas. This is largely
because energy usage fluctuates wildly over the course of a day, and it
is fairly easy to turn turbines on and off at relatively short notice.
That way, when more energy is needed, turbines can be turned on, and
when the usage demands drop back down, those same turbines can be easily
turned off. As I will soon discuss, that's not so easy to do with energy
sources like solar and wind power, which come and go as they please, and
often have peak production patterns which run opposite to usage
patterns.

A Survey of Current Technologies

Because, for the sake of this paper, I am not not
allowing the United States to rely on coal, oil, natural gas, or nuclear
fissile material, we must instead take stock of available alternative
methods of electricity generation. The technologies I will discuss here
are technologies that can be used for the remaining lifetime of the
earth because of where they draw their energy. I will specifically look
at wind, solar, geothermal, and the burning of hydrocarbons such as wood
and dung. First though, I would like to dispel a common myth regarding
these technologies: that they are completely renewable, and therefore
unlimited. These technologies all operate by converting energy that is
currently abundant on the earth and which will never stop being
abundant. However, this requires a physical object be made to affect
this conversion. Accordingly, if the material that goes into the
production of each of these units is not 100% recycled and re-used upon
their being decommissioned, these technologies are also not truly
"renewable." This is because they would still be using up finite
resources (in the form of metal, concrete, or silicon) and discarding
them as waste at the end of their energy-producing lifetimes. While the
energy that these technologies convert into electricity is abundant,
free, and essentially infinite, the physical objects required to do
these operations use up finite resources as hungrily as does the burning
of coal, so these technologies are only as "renewable" as their
production and recycling processes.

The first technology I will look at is solar energy
as manifested by electricity derived mostly from photovoltaic cells and
thermal concentrators, one of the most heavily touted sources of
"renewable" energy. I would first like to make a note that this method
solar energy production is "renewable" in the sense that the sun itself
will never keep assailing the earth with energy in the form of photons
for many more years, and that when it does stop, we will have bigger
problems than fulfilling our energy budget. Looking at Figure 1 below,
we see that the United States receives an average of about
4KWh/m2/day over its entire surface; from this we can
calculate the total amount of solar energy incident upon the United
States every year. [5] The United Nations lists the United State's
surface area as 9.6 × 106 Km2 , so doing
some math we see that the total amount of energy coming from the sun and
striking the United States in 1 year is roughly 5.0 ×
1022 Joules. [4] As we can easily see, this is about 500
times as much as the United State's total energy budget for 2009, which
was 9.5 × 1019 J; so if just 1% of the entire United
States could be covered in solar panels, there'd theoretically be more
than enough electricity to fulfill demand.

Despite this rosy picture of nearly boundless energy,
one of the main downsides to using solar energy is that the amount of
energy produced is proportional to the intensity of the sunlight, so if
it's a cloudy day (or night time) solar arrays won't be producing as
much energy as at peak sunlight hours. What this really means though, is
that regions that rely on air conditioning in the hot summer months will
be at peak usage during peak production times (during the sunniest parts
of hot days), which is good. But colder regions (like the Midwest and
East Coast) have opposite usage patterns since their biggest draw comes
from heating during the cold winter months, when there isn't much sun.

Secondly, I will look at electric energy produced by
wind turbines, another favorite form of "renewable" energy because the
winds will presumably never stop blowing as long as there is life on the
earth. One of the main cited downsides of wind energy is that it too
comes on and off when it pleases, though that issue is softened by the
fact that the wind generally dies slowly, making it relatively easy for
grid operators to shift resources around. According the the US's
National Renewable Energy Lab (NREL), 3.7 &times 107 GWh (1.3
&times 1020 J) of annual potential exists in the United
States. [6] This number is from a report that only takes into account
regions with a certain minimum wind speed and assumes 5MW/Km2 of
installed space. While this number most likely has large error bars, and
was made by a group that supports wind energy, the total production
capacity cited by them is on the order of 1020 J, which is
roughly equal to the US energy budget for 2009. This suggests that wind
energy likely won't be a feasible sole means of energy production, but
it definitely has room for growth beyond its current 0.1% share of
production, and it is slated to grow significantly, if current the
trends outlined in Fig. 2 are any indication.

Taking a look at geothermal energy, we see that 3.5
× 1017 J were produced in 2008 [3] from a slated mean
capacity of roughly 9,057 MW. [7] Looking at untapped resources, we see
an estimated 540,000 MW of additional potential capacity. [7]
Extrapolating from that, we see that geothermal has a potential energy
production of roughly 2.0 × 1019 Joules per year, about
a fifth of current usage. However, that doesn't take into account
small-scale thermal heating used to warm buildings, which is regrettably
poorly documented, but which would further increase geothermal's
potential impact. Geothermal also has the nice property that it's very
constant, which means that it could provide a nice baseline energy that
runs year round.

Lastly, looking at biomass we see the form of energy
production most similar to current combustible fuels. The key difference
though is that biomass can be completely renewable, and have no impact
on foodsources if it comes from:

Energy crops that don’t compete with food crops for land

Portions of crop residues such as wheat straw or corn
stover

Sustainably-harvested wood and forest residues

Lean municipal and industrial wastes [8]

The key here again is that the biomass must be
harvested at sustainable rates, meaning that the harvest rate and
production rate must be equal, or it is again not renewable. One issue
with biomass however, is that it is also used heavily to produce
fertilizers and paper, so it is difficult to greatly expand its use
without risk of unsustainable consumption, or causing ripples in the
food production industry. There is however potential for methane
harvesting from kitchen compost and organic scraps that otherwise go to
landfills, as well as human fecal matter. Estimates say that 5 to 7
million tons of sludge (human fecal matter) were created in the United
States in 2002 [9], and that the dry biomass has an energy density of
10,000BTU/lb. [10] Conservatively guessing that dry biomass is about
half the density of wet biomass, we get about

While this number is by no means accurate, even if I
was off by a factor of 10, this value is still nowhere near making a
significant contribution to the United States' energy budget of
~1020 Joules.

Integration Into The Current Grid

Now that I have shown the energy-producing potential
of solar, wind, geothermal, and biomass energy, we can start to look
into how they could fulfill the raw amount of energy required by the
United States. However, we also need to figure out how to integrate that
power so that it is always readily available at all hours of the day,
every day of the year. This issue is compounded by the problem that
large parts of the country are at peak energy usage when solar is at its
minimum production. One advantage of the current grid is that it relies
heavily on the use of combustibles (ie coal and natural gas) that can be
switched on with short notice. Fortunately, there are a two methods of
storing energy that have been proven effective: hydropump storage
(pushing dam-loads of water up and down hills), and compressing and
storing air underground.

First looking at compressed air, I will take a look
at the United States' only compressed air energy storage facility, in
McIntosh, Alabama. This 110MW facility's "19 million cubic feet [of air]
is stored at pressures up to 1080 psi in a salt cavern up to 2500 feet
deep and can provide full power output for 26 hours." [11] That
translates to

110 &times 106 Watts ×
26 hours × 3600s/hour
= 1.0 × 1013 Joules

of total energy storage capacity. However, there is
only one of these plants in the United States, largely because it is
more profitable to store compressed natural gas in them instead.
However, if the United States' 4364 billion cubic feet of natural gas
storage (in 2010)[12] were all converted to compressed air, that would
yield us with 2.3 × 1018 Joules of potential storage.
At 2.4% of yearly usage (about 9 days' worth), that's not a small amount
of storage capacity to be able to contain at any given time, especially
since there is then the option of re-charging these cites when usage
once more drops below production. While this could easily be used to
provide electricity when consumption increases during peak hours on an
hourly timescale (assuming it was recharged during low-usage night
hours), this would still not be enough energy to keep the coldest parts
of the country lit and warm during the winter months, in the absence of
any other power being produced. Unfortunately, potential for expansion
of these compressed air tanks is fairly limited since they are generally
made from depleted aquifers and hydrocarbon wells, and those aren't
things that can be easily produced on demand.

Next I will look to hydropump storage systems, which
push water up a large hill when there is excess electricity, and release
it back down hill when it is needed. In 2009 the US had 21.5 GW of
hydropump storage capacity, [12] but unfortunately there is no time
scale listed for that 21.5 GW, so there is no way to know how much
energy is represented. However, we can see how this stacks up as a
percentage of average power use. The total energy use for 2009 was 9.5
&times 1019 J, which over the year averages to 3.0 ×
1012 Watts, or 3000 GW. From this we see that our 21.5 GW
only comprises 0.7% of the average power consumed, so we can't expect
stored hydropower to foot the energy bill when all else fails. The US
also seems to have no plans for expanding its hydropump storage capacity
anytime in the foreseeable future, suggesting that it's probably very
expensive to install, and that there probably aren't very many viable
cites to expand capacity to. [12]

The Solution

It would seem that it is possible for the United
States to provide itself with power without the use of any non-renewable
combustible fuels, largely though the use of geothermal, solar, and wind
power for baseline needs, and using compressed air and hydropump storage
to take into account fluctuations on a daily basis. For the issue of
what to do when solar production gets weak in colder regions during
winter, it is likely that solar energy would have to be transported via
transmission lines from sunnier, more temperate regions, which
experience lower than average energy usage during those times. However,
winter usually brings strong winds, and so wind farms should be able to
support much of the baseline energy needs, if managed properly. This
suggests that one solution isn't going to suit the entire United States,
and that distinct approaches will have to be taken on the regional level
to best match usage with production. It also may turn out that the
entire United States may have to integrate to move electric power over
longer distances than it currently does.

There are some specific issues that I did not discuss
- transportation fuel for vehicles, cost, mass production feasibility,
fluctuation numbers, etc - that factor heavily into feasability.
However, the goal of this paper was to ascertain whether or not it would
be physically possible to produce the energy consumed by the United
States currently in the absence of all non-renewable combustible fuels.
As shown, that quantity of energy can be realistically produced through
wind power, can theoretically be produced many times over by solar
power, can be chipped away at by large-scale geothermal (~20%), can be
contributed to by household geothermal for heating purposes
(contribution unknown), and will get roughly 6% from current
(difficultly changed) hydropower and biomass usage. None of that takes
into account new technologies or improvements in current technology
(with the exception of geothermal). Secondly I have shown that daily
power fluctuations can feasibly be buffered through the use of
compressed air storage with some additional capacity coming from
hydropump storage.

These new energy sources cannot be plugged directly
into the current energy grid without some additional storage
infrastructure and clever source choices, but it seems that it would be
possible to do, both from a net production standpoint and a usage
fluctuation standpoint.